In last week's BioNews we published an article about research into possible new treatments for mitochondrial disorders, in which we stated that: 'Sperm do not contribute any mitochondria to the embryo (as they are all present within the tail, which falls off after fertilisation) and, consequently, children inherit all their mitochondrial genes from their mother'.

It has been pointed out to us that it is not entirely correct to state that all of a sperm's mitochondria are present in the tail. Whilst it is true that 'sperm do not contribute any mitochondria to the embryo and, consequently, children inherit all their mitochondrial genes from their mother' it is has been known for a decade that some paternal mitochondria do get into the egg but are selectively destroyed - while this is an interesting biological phenomenon in its own right, it does not alter the maternal inheritance pattern of mitochondrial mutations.